Wholly aromatic polyester resins long have been known. For instance, 4-hydroxybenzoic acid homopolymer and copolymers have been provided in the past. Those wholly aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point. Other amorphous wholly aromatic polyesters when molten frequently exhibit an isotropic melt phase. With the crystalline polymers molding techniques such as compression molding or sintering may be utilized; however, injection molding, melt spinning, etc., commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty.
Representative publications which discuss wholly aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldwell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b), Polyarylates (Polyesters From Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) EQU Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975); and (d) Poly(p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, by Roger S. Storm and Steven G. Cottis, Coating Plast. Preprint, Vol. 34, No. 1, Pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,169,121; 3,321,437; 3,549,593; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,778,410; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487.
In U.S. Pat. No. 3,549,593 identified above is disclosed a polyester comprising recurring units derived from certain substituted hydroxybenzoic acids wherein the substitution is a lower alky group or a lower aryl group.
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anisotropy. See, for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson, Jr., H. F. Kuhfuss and T. F. Gray, Jr., 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat Nos. 838,935 and 828,936, (c) Dutch Pat. No. 7505551, (d) West German Pat. Nos. 2520819, 2520820, 2722120, 2834535, 2834536 and 2834537, (e) Japanese Pat. Nos. 43-223; 2132-116; 3017-692; and 3021-293, (f) U.S. Pat. Nos. 3,991,013; 3,991,014; 4,057,597; 4,066,620; 4,067,852; 4,075,262; 4,083,829; 4,093,595; 4,118,372; 4,130,545; 4,130,702; 4,146,702; 4,153,779; 4,156,070; 4,159,365; 4,161,470; 4,169,933; 4,181,792; 4,183,895; 4,184,996; 4,188,476; 4,201,856; 4,219,461; 4,224,433; 4,226,970; 4,230,817; 4,232,143; 4,232,144; 4,238,598; 4,238,599; 4,238,600; 4,245,082; 4,245,084; 4,247,514; 4,256,624; 4,265,802; 4,267,289; 4,269,965; and 4,279,803 (g) U.K. application No. 2,002,404; and (h) European patent application Nos. 0008855, 0018145. See also U.S. Ser. Nos. 109,575, filed Jan. 4, 1980 (now U.S. Pat. No. 4,285,852); ; 128,759, filed Mar. 10, 1980 (now U.S. Pat. No. 4,299,756) filed July 15, 1980 (now U.S. Pat. No. 4,337,190); and 194,196, filed Oct. 6, 1980 (now U.S. Pat. No. 4,318,841).
It is an object of the present invention to provide a novel wholly aromatic polyester which is capable of forming an anisotropic melt phase.
It is an object of the present invention to provide a wholly aromatic polyester which is capable of readily undergoing melt processing.
It is an object of the present invention to provide an wholly aromatic polyester which may be formed on a relatively economical basis.
It is an object of the present invention to provide a wholly aromatic polyester which is capable of being melt processed using standard equipment commonly selected for the melt processing of polyethylene terephthalate.
It is another object of the present invention to provide a wholly aromatic polyester which is particularly suited for injection molding to form three-dimensional shaped articles, etc.
These and other objects, as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following detailed description.